To enable analysis of the different functional programs of monocytes, human primary monocytes were purified from three to six healthy human donors (depending on experiment) by first isolating peripheral blood mononuclear cells by differential centrifugation over Ficoll-Paque, followed by depletion of T-cells, B-cells and NK-cells with anti-CD3, CD19 and CD56-coated beads, respectively (
Fig. S1). Macrophages (Mf) were obtained by
in vitro culture of the purified monocytes (Mo) for 6 days in cell culture medium enriched with human serum (10%). Monocyte tolerance, a state akin to immune paralysis during bacterial sepsis or endotoxin shock, was induced
in vitro by exposing the purified monocytes to lipopolysaccharide (LPS) for 24 h (9 (
link)). Monocyte training, a functional state in which cells respond more strongly to microbial stimuli that mirrors the non-specific protective effects of live microorganism vaccination (e.g. BCG, measles, yellow fever, (15 (
link))) (
Fig. 1A, B) was induced
in vitro by exposing the purified monocytes to β-glucan for 24 h (
Fig. 1B) (10 (
link)). The LPS or β-glucan was then washed out from the system and the cells were incubated in enriched cell cultured medium for five days.
Saeed S., Quintin J., Kerstens H.H., Rao N.A., Aghajanirefah A., Matarese F., Cheng S.C., Ratter J., Berentsen K., van der Ent M.A., Sharifi N., Janssen-Megens E.M., Huurne M.T., Mandoli A., van Schaik T., Ng A., Burden F., Downes K., Frontini M., Kumar V., Giamarellos-Bourboulis E.J., Ouwehand W.H., van der Meer J.W., Joosten L.A., Wijmenga C., Martens J.H., Xavier R.J., Logie C., Netea M.G, & Stunnenberg H.G. (2014). Epigenetic programming during monocyte to macrophage differentiation and trained innate immunity. Science (New York, N.Y.), 345(6204), 1251086.